Fluid system

ABSTRACT

A fluid system for example for steam raising comprising a flow control device (20), means (28) to supply a head of fluid to the flow control device (20), and at least one fluid using means such as a flash boiler (12-14), the flow control device (20) comprising a chamber (48), an inlet (49) to the chamber from the fluid supply means (28), and an outlet (21-23) from the chamber (48), a valve means (40) associated with the outlet (21-23) operable to direct fluid from the outlet (21-23) either to the fluid using means (12-14) or to a relief means (43-45).

DESCRIPTION OF INVENTION

This invention relates to a fluid system and more particularly, but notexclusively to a fluid system for steam raising. In a steam raisingsystem conventionally there is a flash boiler to which water is fed by apump. The flash boiler provides steam under pressure to a steamaccumulator from where steam may be drawn off for use. The capacity ofthe pump needs to be matched to the capacity of the flash boiler forefficient production of steam.

In such a system where a single flash boiler is provided, the pressureof steam achieved in the steam accumulator is sensed, and when an uppersteam pressure is sensed, the flash boiler is shut down and the pumpdeactivated. When the pressure of steam in the steam accumulator fallsto a second threshold pressure, the flash boiler and pump arereactivated. Necessarily the warm up time is long where there arefrequent such shut downs. Furthermore, the life of the pump can beshortened by frequently switching the pump on and off.

If it is desired to increase the capacity of the system, for example todouble the capacity of the system, it is necessary to provide anadditional pump and flash boiler which can provide steam to the steamaccumulator, or an enlarged steam accumulator if required. In such amultiple flash boiler arrangement, when a first upper threshold pressureis sensed in the steam accumulator, only one of the boilers andassociated pumps are shut down. If the pressure in the system continuesto rise to a second upper threshold pressure, the second flash boilerand pump are deactivated, and so on in systems having more than twoboilers and pumps.

Switching on or off of the boilers and associated pumps may be achievedautomatically via a control means, or manually in response to warningsignals provided to an operator.

An object of the present invention is to provide a new or improved fluidsystem.

According to one aspect of the invention we provide a fluid systemcomprising a flow control device, means to supply a head of fluid to theflow control device, and at least one fluid using means, the flowcontrol device comprising a chamber, an inlet to the chamber from thefluid supply means, and an outlet from the chamber, a valve meansassociated with the outlet operable to direct fluid from the outleteither to the fluid using means or to a relief means.

Thus in a system embodying the invention where a head of fluid isprovided by a pump there is no need to match the capacity of the pump tothe capacity of the system but provided that the pump can deliver morefluid to the fluid control device than required by the or each of thefluid using means, any capacity of pump may be used. However, the outletneeds to be sized to ensure that the amount of fluid fed to the fluidusing means, when the valve means permits this, is that required by thefluid using means.

Preferably the outlet from the chamber is sized so that the pressure inthe chamber is always greater than the pressure downstream of the flowcontrol device so that changes in pressure in the system, e.g. in thefluid using means do not have any significant effect on the pressure inthe chamber and hence on the performance of the pump. Preferably thepressure in the chamber is arranged to be at least twice the maximumpressure downstream of the flow control device e.g. in the fluid usingmeans, but more preferably the pressure in the chamber is even greaterthan this.

Operation of the valve means may be controlled by a control meansresponsive to a sensor means which senses a parameter of the system sothat when a threshold value of the parameter is sensed, the fluid usingmeans is deactivated so that there is no further fluid required, and thevalve means is operated to cause fluid from the outlet of the chamber tobe directed to the relief means so there is no need to deactivate thepump.

In a greater capacity system, the chamber may have a plurality ofoutlets each having an associated valve means operable to direct fluidto an associated fluid using means or to a relief means.

Thus there is no need to have a pump for each fluid using means althoughall of the outlets of the chamber would need to be sized to ensure thateach of the fluid using means receive the required amount of fluid fromthe chamber of the flow control device. Preferably, all of the outletsfrom the chamber of the flow control device are of the same size wherethe fluid using means are all similarly rated.

Each of the valve means may be controlled by a control means responsiveto sensor means sensing a parameter of the system to which all of thefluid using means may contribute. The relief means may comprise aconduit which returns fluid from the or each valve means to a reservoirfrom which fluid may be drawn to supply the head of fluid. The reservoirmay comprise a vessel having an inlet from a fluid source, the amount offluid permitted to enter the vessel via the inlet being controlled by avalve, such as a float control valve, sensitive to the level of fluidwithin the vessel.

The invention is particularly applicable to a fluid system comprising asteam raising system wherein the or each fluid using means may comprisea flash boiler, and the parameter sensed is the pressure of steamproduced by the, or all of the flash boilers.

The system may incorporate a steam accumulator to which steam is fedfrom the or each flash boiler, and the pressure of steam in theaccumulator may be sensed by the sensor means.

Where a single flash boiler only is provided, the control means mayoperate the valve means to deactivate the flash boiler when the pressureof steam in the system, preferably in the steam accumulator whereprovided, reaches an upper threshold pressure, and operate the valvemeans to direct water to the relief means, and the control means mayreactivate the flash boiler again and operate the valve means to directfluid to the flash boiler when a lower threshold steam pressure issensed.

Where a plurality of flash boilers are provided each of the flashboilers may be arranged to be deactivated by the control means in turnwhen an associated threshold pressure is sensed, and the control meansmay be arranged to de-activate and reactivate the flash boilers andoperate the respective valve means in a predetermined sequence to ensurethat each of the flash boilers are used generally equally.

According to a further aspect of the invention we provide a method ofoperating a fluid system in accordance with the first aspect of theinvention, the method comprising the steps of sensing a parameter of thesystem, signalling a control means when an upper threshold value of theparameter is sensed, the control means in response, de-activating thefluid using means and signalling the valve means to direct fluid fromthe outlet of the flow control device to the relief means, andsignalling the control means when a lower threshold valve of theparameter is sensed, the control means in response re-activating thefluid using means and signalling the valve means to direct fluid to thefluid using means.

The invention will now be described with the aid of the accompanyingdrawings in which:

FIG. 1 is a diagrammatic illustration of a fluid system in accordancewith the invention, and,

FIG. 2 is an enlarged illustrative view of part of the system of FIG. 1.

Referring to the drawings, a steam raising system comprises a steamaccumulator 10 from which steam may be drawn off via a supply line 11when required for use.

Steam is supplied to the steam accumulator 10 from, in this examplethree, flash boilers 12,13 and 14 of substantially identical rating.

Each of the flash boilers 12 to 14 incorporate a heating coil 15 throughwhich water passes as it is heated by a burner 16, in the presentexample an oil or gas burner, the products of combustion passing fromthe flash boilers 12,13,14, by respective flues 17 which convenientlyare connected together and to a common flue outlet.

Water is supplied to each of the flash boilers 12,13,14, from a flowcontrol device 20 which will be described in detail hereinafter, thedevice 20 having outlets 21,22,23, each to a respective supply conduit24,25 and 26 through which water may pass from the flow control device20 to the respective flash boiler 12,13,14.

Water is fed to the flow control device 20 from a positive displacementhigh capacity pump 28 which is connected to a water source 29 comprisinga vessel having an inlet 30. The level of water within the vessel 29 iscontrolled by a float control valve 31, and a conduit 32 connects thevessel 29 to the pump 28.

The pressure of steam within the steam accumulator 10 is sensed by asensing means 33 which provides signals to a control means 34 which isarranged to operate as follows.

As the steam pressure in the steam accumulator 10 rises to a first upperthreshold pressure, the control means 34 is arranged to de-activate oneof the flash boilers 12 to 14, for example boiler 12, by signalling theboiler along a line 36. If the steam pressure in the accumulator 10continues to rise, another boiler, for example boiler 13 is de-activatedby a signal passed from the control means 34 along a line 37.

If the steam pressure in the accumulator 10 rises further, for exampleif little or no steam is being drawn off for use, the control means 34de-activates the last boiler 14 by sending a signal along a line 38.

Preferably the sequence in which the boilers 12 to 14 are de-activatedis changed periodically by a sequencer of the control means 34 to ensurethat each of the boilers 12 to 14 are operated generally equally.

As steam is drawn off for use along the supply line 11, the pressurewithin the steam accumulator 10 may fall. As the steam pressure fallsbelow a first threshold pressure, one of the boilers 12 to 14,preferably boiler 12 if de-activated first, is re-activated. As thepressure continues to fall, a further boiler, for example boiler 13, isre-activated, and if the pressure still continues to fall, the finalboiler 14 will be re-activated.

Preferably of course, the boilers 12-14 at least when all activated, areable to produce more steam than is required in line 11 for use.

In practice, all of the boilers 12-14 may not be de-activated before oneor all of the boilers 12-14 are re-activated again. This will depend onthe rate of use of the steam. The boilers 12 to 14 may be activated orde-activated as necessary by the control means 34 to ensure that thepressure in the steam accumulator 10 remains within a predeterminedpressure range so there is always an adequate supply of steam in thesteam accumulator 10.

It can be seen that each outlet 21,22,23, has an associated valve means40,41, and 42 in the respective supply conduit 24,25,26, which in thisexample are solenoid operated valves, also controlled by the controlmeans 34. When the control means 34 signals the boiler 12 to bede-activated, a signal is also sent to valve means 40 so that water isno longer supplied along supply conduit 24 to the flash boiler 12, butis diverted to a relief conduit 43. When a signal is sent from thecontrol means 34 along line 36 to the boiler 12 to cause the boiler 12to be re-activated, a signal is also sent to the valve means 40 to causethe water to again be directed from the supply conduit 24 to the flashboiler 12.

Similarly, the valves 41 and 42 operate either to direct water to therespective flash boiler 13,14, or to an associated relief conduit 44,45.

Each of the relief conduits 43,44, and 45 are arranged to return waterto the vessel 29 so that the water may be recycled, although the excesswater may be disposed of from the conduits 43-45 otherwise as required.

Furthermore, the steam accumulator 10 has an outlet 45 arranged toreturn condensate from the steam accumulator 10 to the vessel 29.

Referring now to FIG. 2, the construction of the flow control device 20can be seen.

The device 20 includes a central chamber 48 to which there is an inlet49 connected to pump 28.

The outlets 21,22 and 23 each comprise an injector nozzle having anorifice of a predetermined size. The pump 28 as hereinbefore mentionedis of large capacity and is arranged to ensure that the water pressurein chamber 48 is always at least twice as great as the maximum pressureattainable by the steam in the steam accumulator 10 by operation of allof the flash boilers 12,13,14. The orifices of each of the outlets21,22,23, are very small and are arranged so water is injected from thechamber 48 into the supply conduits 24,25, and 26 at a predeterminedrate so that the amount of water supplied is that required by therespective flash boiler 12,13,14, to operate efficiently i.e. the nozzleoutlet size is matched to the capacity of the respective boiler12,13,14. Of course, the sizes of all three outlets 21,22, and 23 needto be chosen together to ensure that the correct flow of water to eachof the respective flash boilers 12 to 14 is attained because if the sizeof any one outlet orifice was changed, the supply through the remainingorifices would be effected.

In the present case, the boilers 12,13 and 14 are each of the samerating and hence the nozzle outlets 21,22, and 23 are essentially of thesame size so that an equal quantity of water is fed to each of thesupply conduits 24 to 26.

The construction of the valve means 40 is also illustrated in FIG. 2.

Preferably the valve means 40 comprises a valve 50 in the return conduit43, and a valve 51 in the supply conduit 24 between the outlet 21 andthe flash boiler 12, the two valves 50 and 51 being arranged to operatein tandem so that when valve 50 is open, valve 51 is closed, and viceversa, the valves being solenoid operated in response to a signal fromthe control means 34.

The constructions of the valve means 41 and 42 are similar and the sameparts are labelled with the same reference numerals.

However any other type of valve means which operates to divert watereither to the respective flash boiler or to a relief means may beprovided.

It will be appreciated that the invention provides significantadvantages over conventional systems in which each flash boiler 12 to 14would require its own pump. In the present example, provided that thecapacity of the pump 28 exceeds the total water requirement of the steamraising system, any desired capacity of pump can be used, it only beingnecessary to select the orifice sizes of the outlets 21-23 to match boththe capacity of the pump and the requirement of the associated flashboilers.

If it is desired to increase the capacity of the system still further,it is simply necessary to provide a further outlet from the flow controldevice 20 which would have a valve means to direct fluid either to thefurther flash boiler or to a relief means. However, simply to increasethe capacity of the system in this way the sizes of the nozzles ofoutlets 21 to 23, would need to be changed in order to ensure that thesame quantity of fluid is provided to each of the flash boilers 12 to 14as when only the three outlets shown, are provided.

In a preferred arrangement, a flow control device 20 would be providedhaving a predetermined number of outlets, for example ten outlets. Eachoutlet would already be connected to a supply conduit such as conduits24 to 26, but each of the outlets not in use i.e. not connected to aflash boiler, would be connected to a relief conduit returning the waterfrom the outlet to the vessel 29. As and when required, an additionalvalve means can be installed with one of the previously unused outlets,so that water can be directed to a further flash boiler when required,which could be arranged to contribute to the capacity of the steamraising system. Thus this would not affect the outlets already in use.Of course, the additional valve means would need to be connected to thecontrol means 34, which may need to be reprogrammed. Thus instead of thewater from the previously unused outlet passing to the relief conduit,the water could be fed to the further flash boiler or to the reliefcondition, under the control of the control means 34. In this way, thecapacity of the system may be increased (or decreased) without having tochange the size of any nozzle in any of the outlets of the flow controldevice 20.

Although the invention has been described in relation to a steam raisingsystem having three flash boilers, it will be appreciated that thesystem may be used with a single or two flash boilers only, or anynumber of flash boilers as required, the capacity of the system onlybeing limited by the number of outlets which the flow control device 20may be provided with and the capacity of the pump 28.

Thus the invention provides a modular steam raising system the capacityof which may be simply increased or decreased as required within a largerange, without having to change the capacity of the pump.

Various modifications may be made without departing from the scope ofthe invention. For example, the flash boilers 12 to 14 need not be oilor gas fired as described, but could be electrically fired as desired.Each of the flash boilers may provide steam to its own steam accumulatorif desired which would have its own associated sensor means and controlmeans to control the flash boiler.

Although specifically described in relation to a steam raising systemthe invention may be applied to any fluid system having one or morefluid using means to which fluid must be fed at a predetermined rate tomatch the capacity or rating of the fluid using means. For example, theinvention may be applied to a conventional boiler arrangement or even ahydraulic circuit. Thus the valve means associated with each outlet ofthe flow control device may be operable in response to any sensedparameter of the system downstream of the flow control device, such aswater temperature in a conventional boiler arrangement, or hydraulicpressure, in a hydraulic circuit.

The features disclosed in the foregoing description, in the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the function, or a method orprocess for attaining the disclosed result, or a class or group ofsubstances or compositions, as appropriate, may, separately or in anycombination of such features, be utilised for realising the invention indiverse forms thereof.

I claim:
 1. A fluid system comprising a plurality of water usingboilers, a single pump means, and a flow control device, the flowcontrol device comprising a chamber, an inlet to the chamber, meansconnecting the inlet to the single pump means which supplies a head ofwater to the flow control device, and the flow control device furthercomprising a plurality of outlets, one for each of the water usingboilers, a valve means associated with each outlet, means connectingeach of the outlets to the respective valve means, each valve meansbeing operable to direct water fed thereto from the associated outletalternatively to one of the respective water using boilers and a reliefmeans.
 2. A method of operating a fluid system comprising a plurality ofwater using boilers, a single pump means, and a flow control device, theflow control device comprising a chamber, an inlet to the chamber, meansconnecting the inlet to the single pump means which supplies a head ofwater to the flow control device, and the flow control device furthercomprising a plurality of outlets, one for each of the water usingboilers, a valve means associated with each outlet, means connectingeach of the outlets to the respective valve means, each valve meansbeing operable to direct water fed thereto from the associated outletalternatively to one of the respective water using boilers and a reliefmeans, the method comprising the step of sensing a parameter of thesystem to which each of the boilers contribute, signaling a controlmeans when an upper threshold value of the parameter is sensed, thecontrol means in response deactivating at least one of the boilers andsignaling the associated valve means to direct fluid from the respectiveoutlet of the flow control device to the relief means, the sensor meanssignaling the control means when a lower threshold value of theparameter is sensed, the control means in response reactivating at leastone of the boilers which are inactive, and signaling the respectivevalve means to direct water to the reactivated boiler.
 3. A systemaccording to claim 1 wherein the pump is able to deliver more fluid tothe flow control device than required by any one fluid using means.
 4. Asystem according to claim 1 wherein each of the outlets of the flowcontrol device is sized to ensure that the amount of fluid fed to therespective water using boiler, when the associated valve means permitsthis, is that required by the respective boiler.
 5. A system accordingto claim 4 wherein each outlet from the chamber is sized so that thepressure in the chamber is always greater than the pressure downstreamof the flow control device.
 6. A system according to claim 1 whereineach of the valve means is controlled by a control means responsible toa sensor means which senses a parameter of the system to which all ofthe boilers contribute so that when a threshold value of the parameteris sensed, at least one of the boilers is deactivated, and theassociated valve means is operated to cause water from the respectiveoutlet of the chamber to be directed to the relief means.
 7. A systemaccording to claim 1 wherein all of the outlets from the chamber of theflow control device are of the same size and the boilers are allsimilarly rated.
 8. A system according to claim 1 wherein the reliefmeans comprises a conduit which returns water from each valve means to areservoir from where water is drawn to supply the head of fluid.
 9. Asystem according to claim 1 which comprises a steam raising system eachof the fluid using means comprising a flash boiler.
 10. A systemaccording to claim 9 wherein each of the valve means is controlled by acontrol means responsive to a sensor means which senses the pressure ofsteam produced by the flash boilers so that when a threshold pressure issensed, at least one of the boilers is deactivated and the associatedvalve means is operated to cause water from the respective outlet of thechamber to be directed to the relief means.
 11. A system according toclaim 9 wherein the system incorporates a steam accumulator to whichsteam is fed from the or each flash boiler and the pressure of steam inthe accumulator is sensed by the sensor means.
 12. A system according toclaim 10 wherein the control means is arranged to deactivate andreactivate the flash boilers and operate the respective valve means in apredetermined sequence to ensure that each of the flash boilers are usedgenerally equally.